Refurbish a damaged 4S battery - Do not try this!

I purchased a 5000mA Turnigy Nano-Teck 4S 35C, at Hobbyking for my quad-copter in build.

After a small error, i fried out one the "ground side" cell of my battery with 5 or 6 recharge cycles. So i decided that i dont need right now a 3S battery, so i purchased a 1S Turnigy Battery bundle to repair my damaged one.

So first thing first, remove the damaged cell, was easy with my 80W iron.

The new cell, fortunately was almost the same size,just a little wider and shorter.

Is a Turnigy 5000mA 40C

Cheking Battery Health - OK!

All ok, and alight, now is soldering time.

A final Check.

And the final result.

After 30min, and some tape i finally restore the battery, i spend 12€ in the end. The battery is working, and i know that is not a long life battery, after a over discharge, the renaming 3 cells are stressed, but for a low price and only 2 battery's in my gear that worth the risk. I have some doubts, the cover is insulator tape, and i dont know how she will do in heat. and the C rate, the original turnigy as 35C and the cell that i brought is 40C .

What did you do about charging the battery when one cell might have been at a different state of charge (and hence terminal voltage) to the two remaining cells? How well balance is the battery afetr a few charge discharge cycles?

This is one of the more stupidly dangerous things I've seen posted on this site, and there are a lot of those. Cripple yourself or burn down your house, we don't care, but please don't post lessons in how to commit suicide on these forums (which are so incompetently moderated that things like this are allowed to see the light of day).

Maybe the comments posted here may serve as a warning, to any member who is contemplating repairing a damaged LiPo, that this is an extremely dangerous undertaking that could cause physical harm or potential property damage.

That's not how it works, Coyle. This thing needs to be removed. Newbies will see the nice detailed pictures of this insane technique and will not heed the warnings (warnings after all are all over every last thing these days). This blog has no possible positive value and has the potential to cause serious injury or death. Knowingly leaving this up on a site that claims to be "moderated" is the very definition of reckless and could have some very heavy legal consequences.

What makes this even worse is that replacing a cell in a LiPo is not in itself out of the question, though to do it safely and properly requires equipment, knowledge and skills that the average hobbyist doesn't have. The way this, um, technologically challenged person has done it is almost guaranteed to result in an eventual explosion and/or fire. You all are so hysterically concerned with bad publicity that you get your shorts in a knot whenever someone's Phantom falls down in a public place, yet you de facto encourage something like this? Wow.

Diy Drones is primarily meant to do things and projects by your self and learn from mistakes and is for idiots like my self. This blog is by some one who wants to try some thing which by other standards might be dangerous/wrong. We as Diy Community should not condone such project but at the same time it is Diy project so should be politely pointed.

Instead of repairing a 3S with damaged single cell I would have removed/cancelled the damaged one and used it as 2S if I were to do it or being asked for advice.

So be polite/friendly to people much below your pay grade or you can join site/group of your own caliber. DiyDrones is not for " I know it all type guys".

Good balancer would do the job of first bringing down the voltage difference( cell with higher v) to that of other in stack, once at same voltage it starts charging. Key is Good LiPo charger with separate balancer port.

Also , I am told never to store LiPo fully charged rather 30% charged LiPo has better chance. I have personally experienced puffing of LiPo when fully charged LiPo is stored for long time. These were in default charge condition for more than two years with no ill effect but after I charged them full and then let it unused for a long period made it puff. This makes me believe that I should not have charged them full and let it lie idle .Other might have different opinion. In any case LiPo is dangerous if not understood well.